Electrical gas discharge tube circuit



Dec. 23, 1958 J. H. BEESLEY 2,856,132

ELECTRICAL GAS DISCHARGE TUBE CIRCUIT Filed Oct. 6, 1954 9 Sheets-Sheet 1 F- IG. 1.

HTTO'RNEY Dec. 23, 1958 J. H. BEESLEY ELECTRICAL GAS DISCHARGE TUBE CIRCUIT 9 Sheets-Sheet 2 Filed Oct. 6, 1954 INVE N To? do u! HENRY 8665i 6) T'TORNEY Dec. 23, 1958 l J. H. BEESLEY 2,366,132

ELECTRICAL GAS DISCHARGE TUBE CIRCUIT Filed Oct. 6. 1954 9 Sheets-Sheet 5 FITmWNeY Dec. 23, 1958 J. H. BEESLEY 2,866,132

ELECTRICAL GAS DISCHARGE TUBE CIRCUIT Filed Oct 6, 1954 9 Sheets-Sheet 4 HTTDRhP-ZY Dec. 23, 1958 J. H. BEESLEY 2,866,132

ELECTRICAL GAS DISCHARGE TUBE CIRCUIT Filed Oct. 6, 1954 9 Sheets-Sheet 5 INVENTOR HTTQRNE Dec. 23, 1958 J. H. BEESLEY 2,866,132

' ELECTRICAL GAS DISCHARGE TUBE CIRCUIT Filed 001;. 6, 1954 9 Sheets-Sheet 6 IN V6 N TOR JOHN Hem/R 8665M? HTTOPNEY Dec. 23, 1958 J. H. BEESLEY ELECTRICAL GAS DISCHARGE TUBE CIRCUIT 9 Sheets-Sheet 7 Filed 001;. 6, 1954 PEG] IN E R (/m-pv HENRY B LEY l TTORNEY Filed Oct. 6, 1954 J. H. BEESLEY ELECTRICAL GAS DISCHARGE TUBE CIRCUIT 9 Sheets-Sheet 8 INVENTQR Jomv HENRY Bf6LY Dec. 23, 1958 J. H. BEESLEY 2,856,132

ELECTRICAL GAS DISCHARGE TUBE CIRCUIT Filed Oct. 6, 1954 9 Sheets-Sheet 9 Fig.8 Fig.6

Fig. 2 Fig. 3 Fig. 7 57 Fig. 9

' 5Q 2 9 TRANSLATOR I 12 l n i I 3 Fig. 9

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ksmsma Rscnsnsa REGISTER l Fi .10 10] 102 105 8 .WEJTOR K/OHM HENRY 365615) H TTORNEY United States Patent 2,866,132 ELECTRICAL GAS DISCHARGE TUBE CKRCUIT John Henry Beesley, Coventry, England, assignor to The General Electric Company Limited, London, England Application October 6, 1954, Serial No. 460,667

25 Claims. (Cl. SIS-84.5)

Thi invention relates to electrical circuits employing gas discharge tubes of the kind having at least an anode, a cathode and a trigger electrode. The invention is particularly concerned with such circuits in which cold cathode gas discharge triodes are employed.

It is an object of the present invention to provide an electrical gas discharge tube circuit which has a plurality of input paths and an equal number of output paths that are associated each with a different one of the input paths, and which is adapted to switch a signal occurring on an input path to the associated output path and to Prevent signals occurring, or remaining for longer than a brief period in time, on two or more output paths simultaneously. 7

According to the present invention an electrical gas discharge tube circuit comprises, a plurality of input paths each having a predetermined priority relative to the other input paths, an equal number of output paths, a plurality of first gas discharge tubes, each of the said first gas discharge tubes being associated with a different input path and with adifierent output path and acting when struck to cause a signal to be applied to the appropriate one of the said output paths, a plurality of second gas discharge tubes, each of the said second gas discharge tubes being associated with a different one of the said first gas discharge tubes and acting when struck to inhibit the striking of its associated first gas discharge tube, means for striking each of the said second gas discharge tubes that are associated with input paths of lower priority when a signal is applied to one of the said input paths, means for striking after a short delay the first gas discharge tube which is associated with the input path to which such a signal is applied, and means for striking all the remaining second gas discharge tubes after the said delay.

According to a feature of the present invention means are provided for ascertaining whether two or more of the said first gas discharge tubes are conducting simultaneously and if so for preventing signals occurring, or remaining for longer than a brief period in time, on the associated output paths.

A particular application of the present invention lies in the field of automatic telephony where such circuits may be employed to facilitate access between any one of a plurality of registers and a common translator.

As is well known, a register of this kind may be employed in telephone systems to store information relating to one or more digits of a telephone number. This information, when applied to a translator, is converted, that is translated, into a form which is suitable for establishing a speech current path between the telephone exchange of a calling subscriber and the exchange of the wanted subscriber over a predetermined route.

With such an application each register must be able to signal its information to the translator and derive a translation therefrom, and the process must not be interrupted by the arrival of a calling condition on any other register or registers. Again, on the occurrence of simultaneous calling conditions on two or more registers only one must obtain access to the translator the remaining register or registers being subsequently allowed access one at a time.

Two arrangements in accordance with the present invention Will now be described by way of example with reference to the ten figures of the accompanying drawings in which Figure 1 shows an electrical gating circuit.

Figures 2 and 3 are complementary illustrations of a first gas discharge tube circuit which is in accordance with the present invention.

Figures 4 and 5 are complementary illustrations of a second gas discharge tube circuit which is in accordance with the present invention.

Figure 6 shows a time delay circuit which may be used in conjunction with either of the arrangements shown in Figures 2 and 3 or Figures 4 and 5.

Figure 7 shows a circuit which may be used in conjunction with either of the arrangements shown in Figures 2 and 3 and Figures 4 and 5 to ascertain when a simultaneous switching condition exists and for giving an indication of such a condition.

Figure 8 shows an arrangement which acts in response to such an indication to suppress the said simultaneous switching condition.

Figure 9 shows the manner in which Figures 2, 3, 6, 7 and 8 should be arranged to illustrate diagrammatically the electric circuit of one embodiment of the present invention, and

Figure 10 shows diagrammatically an arrangement in which the electric circuit of Figure 9 is used in conjunction with the gating circuit of Figure 1 in an automatic telephone system to enable three registers to be connected selectively and non-simultaneously to a common translator.

Referring now to Figure 1, the gating circuit there shown comprises three similar gating units. The loads 1, 2 and 3 and the signalling leads 5, 6 and 7 respectively, are associated one with each gating unit and the output lead 4 is common to all three units.

Consider now the gating unit associated with the lead 1. When positive voltage is applied to this lead, the rectifier 8 normally conducts so that the output signal occurring on the lead 4 is only a few volts above earth as determined by the values of resistors 9 and 10. However, if a suitable positive voltage is applied to the lead 5, the rectifier 8 ceases to conduct. The amplitude of the voltage occurring on the output lead 4 consequently rises to a value approaching that of the voltage on lead 1.

The gating circuit of Figure 1 may be utilised in a telephone exchange, as will be described more fully hereinafter with reference to Figure 10 of the drawings, for passing signals supplied by threeregisters that are connected to the leads 1, 2 and 3respectively to a common translator that is connected to the lead 4.

The circuit shown in Figures 2 and 3 employs cold cathode gas discharge triodes and comprises three signal input leads 11, 12 and 13. Three similar gating circuits are provided, these being associated one with each of the leads 1]., 12 and 13. The gating circuit associated with lead 11 comprises the gas triodes 22 and 23 and a potentiometer formed by resistors 25, 26 and 27. This potentiometer is connected between earth and a terminal 28, this terminal being maintained at a positive potential with respect to earth. The gas triode 22 has its anode 24 connected to the junction of resistors 25 and 26. The junction of resistors 26 and 27 is connected to the trigger electrode 20 of the gas triode 23 and to the leads 21b and 11 by way of rectifiers 29 and 30 respectively. The

cathode 19 of the gas triode 23 is connected to the output lead 5 so that when this triode is struck the rise in voltage with respect to earth of its cathode 19, which results from the discharge current flowing through resistor 31, is applied to lead 5.

Similarly the gas triodes 32 and 33 of the two corresponding gating circuit have their cathodes connected to the output leads 6 and 7 respectively, and their trigger electrode circuits connected to the input leads 12 and 13 respectively. The operation of this form of signal gating circuit is described in more detail in the specification of United States patent application Serial No. 458,939.

Connections are taken from the output leads 5, 6 and 7 to the trigger electrode of gas triode 34 over rectifiers 35, 36 and 37. The anode 24 of this gas triode is connected to a terminal 28 which is maintained at a positive potential with respect to earth, and its cathode 19 is connected to the lead 38. A connection is taken from the lead 38 to the trigger electrode circuit of each of the gas triodes 22, 50 and 51 over the rectifiers 39, I

40 and 41 respectively.

The time delay circuit shown in Figure 6 acts to delay for a short time the passage of a voltage signal from any one of the leads 74, 75 or 76 to the lead 21a which is arranged to be connected to the lead 21b of Figure 2. The delay circuit comprises cold cathode gas discharge trlodes 17 and 18 and a resistance capacitance network connected between the cathode 19 of gas triode 17 and the trigger electrode 20 of gas triode 18.

In the circuit represented by Figure 9, the gas discharge tube circuit of Figures 2 and 3 is connected by way of leads 74, 75, 76 and 21b to the leads 74, 75, 76 and 21a respectively of Figure 6. The circuit of Figure 7 is connected by way of leads 5, 6 and 7 to the corresponding leads of Figure 3 and by way of lead 57a to the lead 57 of Figure 8. The functions of the circuits shown in Figures 7 and 8 are described later in the specification.

The operation of the circuit represented by Figure 9 W111 be hereinafter described in its application to telephone systems and in particular to its use in the arrangement shown in Figure 10 to enable non-simultaneous connections between any one of three registers 101, 102 and 103 that are connected to the leads 1, 2 and 3 of Figure 1 and to the leads 11, 12 and 13 respectively of Figure 2, and a translator 104 that is connected to the lead 4 of Figure 1.

It is arranged that when any one of the registers 101, 102 and 103 requires access to the translator 104 the approprlate register causes positive voltage with respect to earth to be applied to the appropriate one ofthe input leads 11, 12 and 13. On a suitable positive voltage being applied to the appropriate one of the output leads 5, 6 or 7 by the gas discharge tube circuit of Figures 2 and 3, a signalling path is established between the register and the translator.

Assuming that the register 102 which is associated with the input lead 12 and with the lead 2 of Figure 1 requires access to the translator, the resulting positive voltage on lead 12 is applied to the lead 75 and hence over the rectifier 15 of Figure 6 to the trigger electrode 20 of the gas triode 17 and is of sufficient value to initiate a discharge between this electrode and its cathode 19. The positive H. T. potential which is applied to each of the terminals 28 is of such a value that when a discharge exist between the trigger electrode and cathode of a gas triode, the triode strikes by transfer of the trigger electrode discharge to its anode to cathode gap. On the gas triode 17 striking the discharge current flows through resistor 42 and raises the cathode voltage to a value which is sufiicient to initiate a discharge when applied to the trigger electrode 20 of the gas triode 18. The network comprising resistor 43 and capacitor 44 acts to delay, for a time dependent upon the values of these elements, the initiation of such a discharge 4 and its consequent transfer to the anode to cathode gap of the gas triode 18. On the gas triode 18 eventually striking its cathode and hence the lead 21a attain a positive voltage with respect to earth by virtue of the discharge current flowing through resistor 45.

The positive voltage on the lead 12 is also applied to the trigger electrode 2% of the gas triode 22 by way of rectifier 46, and to rectifier 47. A discharge is initiated across the trigger electrode to cathode gap of the gas tri- 22, which thereafter transfers to the anode to cathode gap. The voltage across the latter gap falls with the result that the voltage at the junction of resistors 26 and 27 falls to a value which is insufficient to initiate a discharge between the trigger electrode and cathode of the gas triode 23. The striking of the gas triode 23 is thus inhibited and the occurrence of an output voltage on the lead 5 is prevented. The register 101 which is associated with leads 1 and 11 is thus prevented from obtaining access to the translator.

After the delay period positive voltages from the leads 12 and 2112 are applied simultaneously to the rectifiers 47 and 48 respectively which are thus biassed to a nonconducting condition. A voltage is therefore applied between the trigger electrode and cathode of the gas triode 32 which is of sufiicient amplitude to initiate a discharge between these electrodes, this voltage being derived from the associated potentiometer. .On the gas triode 32 striking its cathode voltage rises as also does the voltage of the output lead 6 and in consequence the voltage across the trigger electrode to cathode gap of the gas triode 34. On the gas triode 34 striking the voltage developed across its cathode resistor 49 is applied between the lead 38 and earth. A discharge is consequently initated across the trigger electrode to cathode gap of each of the gas triodes 50 and 51 which therefore strike. The striking of the gas triode 50 is of no consequence since the gas triode 32 has been struck previously. The striking of the gas triode 51 inhibits the striking of the gas triode 33 and so prevents the switching of positive voltage signals from the input lead 13 to the output lead 7. The high priority register 103 associated with the leads 3 and 13 is thus prevented from obtaining access to the translator at this stage.

It will be appreciated from the above that there is a small period of time between the application of the positive potential to the input lead 12 and the striking of the gas tricdes 50 and 51. If during this period of time a calling condition occurs in the high priority register 103, the resultant potential on the input lead 13 strikes the gas triode 50, the gas triode 22 having been previously struck by the original calling condition. Two possibilities now arise, these being as follows:

If the gas triode 32 has not previously struck then it is prevented from doing so by the striking of the gas triode 50 whereafter the circuit continues to operate in substantially the same manner as described above with the exception that the gas triode 33 now strikes, the high priority register 103 taking precedence. If on the other hand the gas triode 32 has already struck then the gas triode 33 will strike also and result in the simultaneous occurrence of output signals on the leads 6 and 7.

The function of the circuit shown in Figure 7 is to determine when such a condition exists, the leads 5, 6 and 7 of this figure being connected to the corresponding leads of Figure 3. If, as in the case under consideration,

positive voltages occur simultaneously on the output leads 6 and 7, the rectifier 52 is biassed to a non-conducting condition and the voltage on lead 7 is applied over the resistor 53 and rectifier 54 to the trigger electrode of the gas triode 55 which consequently strikes. Similar arrangements are provided for each combination of two leads from the output leads 5, 6 and 7. When the gas triode 55 strikes the resultant discharge current flows through resistor 56 and causes the lead 57a to attain a positive voltage with respect to earth. The occurrence of this positive voltage is arranged to cause the positive H. T. potential which is applied to each of the terminals 23 to be momentarily discontinued or so reduced in value as to result in the extinction of all the gas triodes previously struck, and so clear the circuit. Re-application of the H. T. potential supply to the terminals 28 permits the register which is of highest priority and which requires access to the translator, to obtain such connection in the manner previously described.

When it is required to terminate a connection between a register and the translator it is arranged that positive voltages are applied simultaneously to the leads 58 and 59. A discharge is thus initiated across the trigger electrode to cathode gap of the gas triode 55 which therefore strikes. A momentary discontinuation of reduction in value of the H. T. potential which is applied to the terminals 28 ensues and the circuit is cleared ready for use in connection with a further calling condition in a register.

One arrangement for discontinuing or reducing the value of the H. T. potential supply is shown in Figure 8 and comprises two thermionic triode valves 60 and 61 which are arranged to operate as a mono-stable multivibrator. In the absence of positive voltage on the lead 57 the triode 60 is conducting and the triode 61 is cut off. The potential on the control grid of the thermionic pentode valve 62 is such that this valve is cut off. The positive H. T. potential on the terminal 28 is derived from a high potential supply line 63 through the thermionic beam tetrode valve 64 which is normally conducting. The terminal 28 of this figure is arranged to be connected to each of the terminals 28 shown in the drawings of Figures 2 to 7.

0n the application of a positive voltage on the lead 57, this lead being connected to lead 57a of Figure 7, the triode 61 commences to conduct andthe triode 60 is cut off. The sharp rise in anode voltage of the triode 60 is applied over the capacitor 66 to the control grid of the pentode valve 62 which commences to conduct, its anode current passing through the resistor 65. The resultant fall in voltage on the control grid of the beam tetrode valve 64 causes this valve to cut ofr thus discon necting the terminal 28 from the H. T. potential supply line 63. When the multi-vibrator subsequently reverts to its stable state, the H. T. potential supply to the terminal 28 is restored by a reversal of the process described above.

Although in the circuit shown in Figures 2 and 3 three signalling paths are provided it should be understood that the invention is not limited to this number, although preferably not more than five such paths are incorporated in a single circuit of thiskind.

When it is required to provide a large number of signalling paths, two or more gas discharge tube circuits, each according to the present invention and each having a predetermined priority relative to the other circuits, may be combined together, means being provided for inhibiting the operation of all gas discharge tube circuits of lower priority when a signal occurs on an input path of any one of the said gas discharge tube circuits, and further means being provided which act after a short delay to inhibit the operation of all the said gas discharge tube circuits which are of higher priority.

Facilities may also be provided for ascertaining when the conditions in one or more of the gas discharge tube circuits are such as to enable signals to occur simultaneously on two or more output paths and if so for suppressing these conditions.

A gas discharge tube circuit Which incorporates the above features is shown in Figures 4 and 5. The circuit there illustrated comprises three gas discharge tube circuits of the kind shown in Figures 2 and 3 these being represented in block form and referenced 67, 68 and 69. The various connections to these circuits correspond in each case to the leads shown in Figures 2 and 3 and are referenced accordingly for gas tube circuit 68. Each of these gas tube circuits 67, 68 and 69 is provided with a circuit of the kind shown in Figure 7 these being represented in block form and referenced 88, 89 and 90 respectively. A single delay circuit of the kind shown in Figure 6 is also provided and is represented in block form and referenced 81, the various connections to the delay circuit 81 having the same reference as in Figure 6.

Referring now to Figures 4 and 5, the input leads such as leads 11, 12 and 13 are each connected over a rectifier, such as the rectifiers 70, 71 and 72 to the trigger electrode 20 of a cold cathode gas discharge triode 73. An output lead 74, 75 or 76 is taken from the cathode 19 of each of these gas triodes to. the delay circuit 81. The delay circuit output lead 21a is connected over the rectifiers 77, 78 and 79 to the gas tube circuits 67, 68 and 69 respectively.

As in the case of the circuit shown in Figures 2 and 3, each of the gas discharge tubes is a cold cathode gas discharge triode and the positive H. T. potential which is applied to each of the terminals 28 is of such a value that when a discharge is initiated across the trigger electrode to cathode gap of a. tube it strikes by transfer of the discharge to its anode to cathode gap. Furthermore each gas triode is provided with a resistor connected between its cathode and earth, the voltage developed across which by the discharge current of its associated gas triode, when struck, being suflicient to initiate a trigger electrode to cathode discharge when applied between these electrodes.

In the second arrangement to be described, the gas discharge tube circuit of Figures 4 and 5 is connected by way of leads such as the leads 5, 6 and 7, to the corresponding leads of a gating circuit of the kind shown in Figure 1, this gating circuit comprising nine similar gating units which are all associated with the same common output lead such as the lead 4.

The operation of this arrangement will be described in its application to telephone systems and in particular to the provision of non-simultaneous connection between any one of nine registers (not shown) that are connected to leads such as the leads 1, 2 and 3 of Figure 1 and to leads such as the leads 11, 12 and 13 of Figure 4, and a translator (not shown) that is connected to a lead such as the lead 4 or Figure 1.

As with the first arrangement, a register requiring access to the translator causes positive voltage with respect to earth to be applied to the appropriate one of the input leads such as the leads 11, 12 and 13. On a suitable positive voltage being applied to the appropriate one of the output leads such as the leads 5, 6 and 7 by the gas discharge tube circuit of Figures 4 and 5, a signal path is established between the register and the translator.

Assuming that the register which is associated with the input lead 12 requires access to the translator: the positive voltage occurring on lead 12 is applied to the gas discharge tube circuit 68 and to the trigger electrode 28 of the gas triode 73 by way of rectifier 71. This voltage is arranged to be of sufficient amplitude to initiate the striking of the gas triode 73. On this gas triode striking the output voltage from its cathode is applied to the lead '75 and thence to the delay network 81 and to the lead 80a of the low priority gas discharge tube circuit 67. The application of this voltage to the lead 80a prevents the switching of positive voltage signals to any of the output leads of the gas discharge tube circuit 67 in the manner previously described. In the gas discharge tube circuit 68 the positive voltage on lead 12 prevents the occurrence of an output signal on the lead 5 in the manner previously described.

After a time determined by the delay circuit 81, the lead 21a attains a positive voltage with respect to earth. This voltage is applied over the rectifiers 77, 78 and 79 to the leads corresponding to the lead 21b of the gas discharge tube circuit 68. The voltage applied over the rectifier 77 is of no consequence since the operation of the gas discharge tube circuit 67 has been previously inhibited. The voltageapplied over the rectifier 79 is of no consequence unless one oimore of the registers associated with the input leads 82, 83 or 84 of the high priority gas discharge tube circuit '69 has received a calling condition during the delay period. This possibility will be considered later. The voltage applied over the rectifier 78 to the lead 21b results in the occurrence of a positive voltage signal on the output lead 6. This voltage signal acts in the manner previously described to prevent the occurrence of a positive voltage signal in the output lead 7 and also to enable the register associated with the lead 12 to obtain access to the translator.

The positive voltage on the 'output lead 6 is applied to the trigger electrode circuit of the gas triode and initiates the striking of this tube. On the gas triode 85 striking the resultant positive voltage on its cathode initiates the striking of the gas triode 1%. On the gas triode 86 striking, the resultant positive voltage on its cathode and consequently on the lead 87 is applied to the leads 80a, 89b and 800, these corresponding to the lead 80 of Figure 2. The registers associated with the high riority gas discharge tube circuit '69 and with the lead 13 of the gas discharge tube circuit 63 are thus prevented from obtaining access to the translator at this stage in the manner previously described.

If during the interval between application of the positive voltage signal to the input lead 12 and the occurrence of the positive voltage on the lead 87 a calling condition occurs in a register of higher priority than the register associated with the input lead 12, as for example the register associated with the input lead 84, then two possibilities arise which are as follows.

if in the gas discharge tube circuit 68 the gas triode 32 has not previously struck then it is prevented from doing so by the striking of the gastriode 50. The circuit operations then proceed as if the positive potential has been applied to the lead 84 only, the register associated with this lead obtaining access to the translator.

If the gas triode 32 has already struck positive voltages occur on both of the leads 6 and 91. As a result of these voltages the gas triodes 85 and 92 strike thereby applying positive voltages to the leads 94 and 95. The leads 94 and 95 are connected, together with the lead 93, to a coincidence gating circuit which is represented in block form and referenced 96. This circuit 96 is identical with that described in connection with Figure 7. The positive voltages on the leads 94 and 95 result in a positive output voltage from the gating circuit 96 over the lead 97, and the gas triode 98 consequently strikes. The resulting positive voltage on the cathode of this gas triode is applied over the lead 5712, which is arranged to be connected to the lead 57 of the circuit shown in Figure 8. The H. T. potential on each of the terminals 28 is momentarily discontinued in the manner previously described and the struck gas triodes are extinguished. Re-application of the H. T. potential supply permits the register which is of highest priority and which requires access to the translator to obtain such connection.

Had the simultaneous switching condition originated from registers associated with the same gas discharge tube circuit, such as the circuit 63, then the output voltage signal resulting from the associated coincidence gating circuit 8h would have initiated in the striking of the gas triode 98 with the consequent momentary discontinuation of the H. T. potential supply.

With an arrangement of the kind described above the number of devices (registers) which may work to one single item of equipment (translator) is considerably increased. Thus by employing five gas discharge tube circuits of the kind shown in Figures 2 and 3, each circuit having five inputs, it is possible to facilitate nonsimultaneous connections between twenty-five devices (registers) and a common item of equipment (translator). When it is required to provide such facilities for a very large number of devices (registers) it may be found necessary to combine several circuits of the kind shown in Figures 4 and 5 in a similar manner to that employed originally to evolve the arrangement shown in these figures, such combinations being within the scope of the present invention.

I claim:

1. An electrical circuit comprising a plurality of gas discharge tubes that each have an anode, a cathode and a trigger electrode, a plurality of pairs of terminals equal in number to the gas discharge tubes, the said pairs having a predetermined order of priority and each pair comprising an input terminal and an output terminal, each gas discharge tube having its cathode connected to a different one of the output terminals and acting when operated to conduct across its anode to cathode discharge gap so as to cause an electric signal to be applied to the associated output terminal, means which connects the input terminal of each pair to the trigger electrode of the gas discharge tube that has its cathode connected to the output terminal of the pair and which responds to the electrical actuation of any one of the input terminals to operate, after a predetermined delay, the gas discharge tube connected to the actuated input terminal, a plurality of inhibiting means which are equal in number to the gas discharge tubes and which are each con-- nected to the trigger electrode of a different one of those tubes, each inhibiting means acting when operated to prevent the operation of the particular gas discharge tube to which it is connected but having no effect if that gas discharge tube is already operated, means which connects the input terminal of each pair, other than the pair of lowest priority, to all the inhibiting means associated with pairs of terminals that are of lower priority and which responds to the electrical actuation of any input terminal to which it is connected so as to operate the inhibiting means associated with all pairs of terminals of lower priority than the pair including the actuated input terminal, and means which connects the output terminals to the inhibiting means and which responds to the operation of any one of the gas discharge tubes so as to operate any of the inhibiting means not already operated.

2. An electrical circuit according to claim 1 in which there is provided means which is connected to the output terminals, to the anodes of said gas discharge tubes and to the inhibiting means and which operates upon the simultaneous occurrence of electric signals on the output terminals resulting from the operation of any two of the said gas discharge tubes to extinguish the anode to cathode discharge in each of the operated gas discharge tubes and to restore each of. the inhibiting means to its non-operated condition.

3. An electrical circuit according to claim 1 in which each gas discharge tube has individual resistance means connected to its cathode and in series with its anode to cathode discharge gap to derive a voltage signal from the discharge current that flows across the said gap when the gas discharge tube is operated which voltage signal constitutes the said electric signal that is applied to the associated output terminal.

4. An electrical circuit according to claim 1 in which the said means, which responds to the eiectrical actuation of any one of the input terminals to operate, after a predetermined delay, the gas discharge tube connected to the actuated input terminal, comprises an electric signal delay circuit having an input and an output, and a plurality of coincidence signal gating circuits which are equal in number to the said pairs of terminals and which are each associated with a different one of the gas discharge tubes, the signal delay circuit having its input connected to each of the input terminals and acting upon the actuation of any one of the input terminals to apply a signal to its output after a predetermined delay, and each said gating circuit having a first input-connected to the assoestates"- 9 ciated input terminal, a second input connected to the output of the signal delay circuit and an output connected to the trigger electrode of the associated gas discharge tube and acting upon the coincidence of signals on its first and second inputs resulting from the actuation of the input terminal connected to its first input to operate the associated gas discharge tube provided that the inhibiting means connected to the trigger electrode of that gas discharge tube is not previously operated.

5. An electrical circuit according to claim 4 in which each said inhibiting means comprises a potentiometer which, during operation, is connected between the positive and negative terminals of the circuit power supply,

a second gas discharge tube which has an anode, a cathode and a trigger electrode and'which is connected with its anode to cathode discharge gap in shunt with a portion of the potentiometer so as when operated to reduce appreciably the voltage drop over that portion of the potentiometer across which it is connected, and a connection from a point on the said shunted portion of potentiometer to a third input of the associated coincidence signal gating circuit, the voltage applied to the output of any one of the said coincidence signal gating circuits upon the said coincidence of signals on its first and second inputs being dependent upon the voltage then applied to its third input and is sufiicient to operate the associated first said gas discharge tube unless the second gas discharge tube of the associated inhibiting means is operated.

6. An electrical gas discharge tube circuit according to claim 5 in which the second gas discharge tubes are cold cathode gas discharge triodes.

7. An electrical gas discharge tube circuit according to claim 1 in which the gas discharge tubes are cold cathode gas discharge triodes.

8. An electrical circuit comprising a plurality of gas discharge tubes that each have an anode, a cathode and a trigger electrode, a plurality of pairs of terminals, the said pairs having a predetermined order of priority and each pair comprising a first input terminal and a second input terminal, an output terminal common to all the said pairs, means which connects each first input terminal to the trigger electrode of a different one of said gas discharge tubes and which responds to the electrical actuation of any one of the first input terminals to operate, after a predetermined delay, the gas discharge tube connected to the actuated first input terminal, means which is connected to the cathodes of said gas discharge tubes, to the second input terminals and to the output terminal and which acts to pass electric signals to the output terminal from the second input terminal of any pair only of the gas discharge tube connected, as aforesaid, to the first input terminal of that pair is operated, a plurality of inhibiting means which are each connected to the trigger electrode of a different one of said gas discharge tubes, each inhibiting means acting when operated to prevent the operation of the particular gas discharge tube to which it is connected but having no'efiect if that gas discharge tube is already operated, means which connects the first input terminal of each pair, other than the pair of lowest priority, to all the inhibiting means associated with the pairs of terminals that are of lower priority and which responds to the electrical actuation of any first input terminal to which it is connected so as to operate the inhibiting means associated with all pairs of terminals of lower priority than the pair including the actuated first input terminal, and means which connects the cathodes of the gas discharge tubes to the inhibiting means and which responds to the operation of any one of the gas discharge tubes so as to operate any of the inhibiting means not already operated.

9. An electrical circuit according to claim 8 in which there is provided means which is connected to the cathodes of said gas discharge tubes and to the inhibiting means and which acts upon the operation of more than one of the said gas discharge tubes to extinguish the dis' charge in each of those gas discharge tubes and to restore each of the inhibiting means to its non-operated condition.

10. An electrical circuit according to claim 8 in which the said means, which responds to the electrical actuation of any one of the first inputterminals to operate, after a predetermined delay, the gas discharge tube connected to the actuated first input terminal, comprises an electric signal delay circuit having an input and an output and a plurality of coincidence signal gating circuits which are equal in number to the said pairs of terminals and which are each associated with a different one of the gas dis charge tubes, the signal delay circuit having its input connected to each of the first input terminals and acting upon the actuation of any one of the first input terminals to apply a signal to its output after the predetermined delay, and each said gating circuit having a first input connected to the associated first input terminal, a second input connected to the output of the signal delay circuit and an output connected to the associated gas discharge tube and acting upon the coincidence of signals on its first and second inputs resulting from the actuation of the first input terminal connected to its first input to operate the associated gas discharge tube provided that the inhibiting means connected to that gas discharge tube is not already operated.

11. An electrical circuit according to claim 10 in which each said inhibiting means comprises a potentiometer which, during operation, is connected between the positive and negative terminals of the circuit power supply, a second gas discharge tube which has an anode, a cathode and a trigger electrode and which is connected with its anode to cathode discharge gap in shunt with a portion of the potentiometer so as when operated to reduce appreciably the voltage drop over that portion of the potentiometer across which it is connected, and a connection from a point on the said shunted portion of the potentiometer to a third input of the associated coincidence signal gating circuit, the voltage applied to the output of any one of the said coincidence signal gating circuits upon the said coincidence of signals on its first and second inputs being dependent upon the voltage then applied to its third input and is sufficient to operate the associated first said gas discharge tube unless the second gas discharge tube of the associated inhibiting means is operated.

I 12. An electrical gas discharge tube circuit according to claim 11 in which the second gas discharge tubes are cold cathode gas discharge triodes.

13. An electrical circuit according to claim 8 in which the gas discharge tubes are cold cathode gas discharge triodes.

14. An electrical circuit which employs gas discharge tubes that each have an anode, a cathode and a trigger electrode and which includes a signal delay circuit having an input and an output and acting upon the electrical actuation of its input to apply a signal to its output after a predetermined delay, and a plurality of switching units having a predetermined order of priority, each switching unit comprising an input terminal connected to the input side of the signal delay circuit, an output terminal, a first said gas discharge tube having its cathode connected to the associated output terminal, indi vidual resistance means that is connected to the cathode and in series with the anode to cathode discharge gap of the first gas discharge tube to derive a voltage signal from the discharge current that flows across the said gap When the first gas discharge tube is operated, a coincidence signal gating circuit which has a first input that is connected to the associated input terminal, a second input that is connected to the output of the delay circuit, a third input and an output that is connected to the trigger electrode of the associatedfirst gas discharge tube and which acts upon the coincidence of signals on its first and second inputs resulting from the electrical actuation of the associated input terminal to gate the signal then occurring on its third input to its output, a potentiometer to derive a striking voltage from the circuit power supply which voltage, applied to the trigger electrode of the associated first gas discharge tube, is sufiicient to initiate the operation of that gas discharge tube, a connection between the potentiometer and the third input of the associated signal gating circuit to apply the said striking voltage to the said third input, and a second said gas discharge tube which is connected with its anode to cathode discharge gap in shunt with a portion of the associated potentiometer that includes the connection to the said third input and which acts when operated as a relatively low resistance shunt across the said portion of the potentiometer to reduce the voltage applied to the said third input below the value of the said striking voltage, the gas discharge tube circuit also including means which connects the input terminal of each switch ing unit, other than the switching unit of lowest priority, to the trigger electrodes of the second gas discharge tubes in all switching units of lower priority and which responds to the actuation of any input terminal to which it is con nected to apply a striking voltage to the trigger electrode of the second gas discharge tube in every switching unit of lower priority than the switching unit including the actuated input terminal, and means which connects the. output terminals to the trigger electrodes of the second gas discharge tubes and which responds to the voltage signal applied to an output terminal when its associated first gas discharge tube is operated to apply a striking voltage to the trigger electrode of each of the second gas discharge tubes.

15. An electrical circuit according to claim 14 in which there is provided means which is connected to the output terminals, to the anodes of the first gas discharge tubes and to the potentiometers and which operates upon the occurrence of the said voltage signals on any two or" the output terminals simultaneously to reduce the value of the voltage applied to the anodes of the said first and second gas discharge tubes below the anode to cathode discharge maintaining value for an interval in time greater than the (lo-ionisation time of any of those gas discharge tubes.

16. An electrical circuit according to claim 14 in which the said gas discharge tubes are cold cathode gas discharge triodes.

17. An electrical circuit which employs gas discharge tubes that each have an anode, a cathode and a trigger electrode and which includes a signal delay circuit having an input and an output and acting upon the electrical acs tuation of its input to apply an electric signal to its output after a predetermined delay, an output terminal, a plurality of signal gating units connected to the output terminal, each said gating unit having a first input and second input and each gating unit acting upon the application of a first voltage signal to its second input to gate an electric signal occurring on its first input to the said output terminal, and a plurality of switching units which are equal in number to the said gating units and which have a predetermined order of priority, each of the said switching units being associated with a different one of the said gating units and comprising an input terminal connected to the input side of the signal delay circuit, a first said gas discharge tube having its cathode connected to the second input of the associated signal gating unit, individual resistance means that is connected to the cathode and in series with the anode to cathode discharge gap of the first gas discharge tube to derive the said voltage signal from the discharge current that flows across the said gap when the first gas discharge tube is operated, a coincidence signal gating circuit which has a first input that is connected to the associated input terminal, a second input that is connected to the output side of the signal delay circuit, a third input and an output that is connected to the trigger electrode of the associated first gas discharge tube and which acts upon the coincidence of signals on its first and second inputs resulting from the electrical actuation of the associated input terminal to gate the signal then occurring on its third input to its output, a potentiometer to derive a striking voltage from the circuit power supply which voltage, applied to the trigger electrode of the associated first gas discharge tube, is sufiicient to initiate the operation of that gas discharge tube, a connection between the potentiometer and the third input of the associated signal gating circuit to apply the said striking voltage to the said third input, and a second said gas discharge tube which is connected with its anode to cathode discharge gap in shunt with a portion of the associated potentiometer that includes the connection to the said third input and which acts when operated as a relatively low resistance shunt across the said portion of the potentiometer to reduce the voltage applied to the said third input below the value of the said striking voltage, the gas discharge tube circuit also including means which connects the input terminal of each switching unit, other than the switching unit of lowest priority, to the trigger electrode of the second gas discharge tube in every switching unit of lower priority and which responds to the actuation of the input terminal to which it is connected to apply a striking voltage to the trigger electrode of the second gas discharge tube in all switching units of lower priority than the switching unit including the actuated input terminal, and means which connects the cathodes of the first gas discharge tubes to the trigger electrodes of the second gas discharge tubes and which responds to the said first voltage signal to apply a striking voltage to the trigger electrode of each of the second gas discharge tubes.

18. An electrical circuit according to claim 17 in which there is provided means which is connected to the anodes and cathodes of the first gas discharge tubes and to the potentiometers and which operates upon the, occurrence of the said first voltage signal at any two of those cathodes simultaneously to reduce the value of the voltage applied to the anodes of the first and second gas discharge tubes below the anode to cathode discharge maintaining value for an interval in time greater than the de-ionisation time of any of those gas discharge tubes.

19. An electrical circuit according to claim 17 in which the said first and second gas discharge tubes are cold cathode gas discharge triodes.

20. An electrical circuit which employs gas discharge tubes that each have an anode, a cathode and a trigger electrode and which includes a signal delay circuit having an input and an output and acting upon the electrical actuation of its input to apply a signal to its output after a predetermined delay, and a plurality of switching units that are arranged in groups, the groups of switching units and the switching units of each group having a predetermined order of priority and each said switching unit comprlsmg an input terminal connected to the input side to the signal delay circuit, an output terminal, a first said gas discharge tube having its cathode connected to the associated output terminal, individual resistance means that is connected to the cathode and in series with the anode to cathode discharge gap of the associated first gas discharge tube to derive a voltage signal from the discharge current that flows across the said gap when that first gas discharge tube is operated, a coincidence signal gating circuit which has a first input that is connected to the associated input terminal, a second input that is connected to the output side of the signal delay circuit, a third input and an output that is connected to' the trigger electrode of the associated first gas discharge tube and which acts upon the coincidence of signals on its first and second in uts resulting from the electrical actuation of the associated input terminal to gate the signal then occurring at its third input to its output, a potentiometer to derive a striking voltage from the circuit power supply which voltage, applied to the trigger electrode of the associated first gas discharge tube, is suificient to initiate the operation of that gas discharge tube, a connection between the potentiometer and the third input of the associated signal gating circuit to apply the said striking voltage to the said third input and a second said gas discharge tube which is connected with its anode to cathode gas discharge gap in shunt with a portion of the associated potentiometer that includes the connection to the said third input and which acts when operated as a relatively low resistance shunt across the said portion of the potentiometer to reduce the voltage applied to the said third input below the value of the said striking voltage; each group of switching units having means which connects the input terminal to each switching unit in the group, other than the switching unit of lowest priority, to the trigger electrodes of the second gas discharge tubes in all switching units in the group that are of lower priority and which responds to the electrical actuation of any one of the input terminals to which it is connected to apply a striking voltage to the trigger electrodes of the second gas discharge tubes in all switching units in the group that are of lower priority than the particular switching unit having its input terminal actuated, and the gas discharge tube circuit also including means which connects the input terminals of each group of switching units, other than the group of lowest priority, to the trigger electrodes of the second gas discharge tubes in all groups of lower priority and which responds to the electrical actuation of any one of the input terminals to which it is connected to apply a striking voltage to the trigger electrodes of the second gas discharge tubes in all groups that are of lower priority than the particular group including the actuated input terminal, and means which connects the output terminals to the trigger electrodes of the second gas discharge tubes and which responds to the voltage signal applied to an output terminal when its associated first gas discharge tube is operated to apply a striking voltage to the trigger electrodes of the second gas discharge tubes in every group.

21. An electrical circuit according to claim 20 in which there is provided means which is connected to the output terminals, to the anodes of the first gas discharge tubes and to the potentiometers and which operates upon the occurrence of the said voltage signals on any two of the output terminals simultaneously to reduce the value of the voltage applied to the anodes of the said first and second gas discharge tubes below the anode to cathode discharge maintaining value for an interval in time greater than the de-ionisation time of any of those gas discharge tubes.

22. An electrical circuit according to claim 20 in which the said first and second gas discharge tubes are cold cathode gas discharge triodes.

23. An electrical circuit which employs gas discharge tubes that each have an anode, a cathode and a trigger electrode and which includes a signal delay circuit having an input and an output and acting upon the electrical actuation of its input to apply an electric signal to its output after a predetermined delay, an output terminal, a plurality of signal gating units connected to the output terminal, each said gating unit having a first input and a second input and each said gating unit acting upon the application of a first voltage signal to its second input to gate an electric signal occurring on its first input to the said output terminal, and a plurality of switching units which are arranged in groups and which are each associated with a different one of the gating units, the groups of switching units and the switching units of each group having a predetermined order of priority and each said switching unit comprising an input terminal connected to the input of the signal delay circuit, a first said gas discharge tube having its cathode connected to the second input of the associated gating unit, individual resistance means that is connected to the cathode and in series with the anode to cathode discharge gap of the associatedfirst gas discharge tube to derive a first voltage signal from the discharge current that flows across the said gap when that first gas discharge tube is operated, a coincidence signal gating circuit which has a first input that is con-- nected to the associated input terminal, a second input that is connected to the output of the signal delay circuit, a third input and an output that is connected to the trigger electrode of the associated first gas discharge tube and which acts upon the coincidence of signals on its first and second inputs resulting from the electrical actuation of the associated input terminal to gate the signal then occurring on its third input to its output, a potentiometer to derive a striking voltage from the circuit power supply, which voltage, applied to the trigger electrode of the associated first gas discharge tube, is sufficient to initiate the operation of that gas discharge tube, a connection between the potentiometer and the third input of the associated signal gating circuit to apply the said striking voltage to the said third input, and a second said gas discharge tube which is connected with its anode to cathode discharge gap in shunt with a portion of the associated potentiometer that includes the connection to said third input and which acts when operated as a relatively low resistance shunt across the said portion of the potentiometer to reduce the voltage applied to the said third input below the value of the said striking voltage; each group of switching units having means which con meets the input terminal to each switching unit in the group, other than the switching unit of lowest priority, to the trigger electrodes of the second gas discharge tubes in all switching units in the group that are of lower priority and which responds to the electrical actuation of any one of the input terminals to which it is connected to apply a striking voltage to the trigger electrodes of the second gas discharge tubes in all switching units or the group that are of lower priority than the particular switching unit having its input terminal actuated, and the gas discharge tube circuit also including means which connects the input terminals of each group of switching units, other than the group of lowest priority, to the trigger electrodes of the second gas discharge tubes in all groups of lower priority and which responds to the electrical actuation of any one of the input terminals to which it is connected to apply a striking voltage to the trigger electrodes of the second gas discharge tubes in all groups that are of lower priority than the particular group including the actuated input terminal, and means which connects the cathodes of the first gas discharge tubes to the trigger electrodes of the second gas discharge tubes and which responds to the occurrence of the said first voltage signal at any one of those cathodes to apply striking voltage to the trigger electrode of each second gas discharge tube in every group.

24. An electrical circuit according to claim 23 in which there'is provided means which is connected to the anodes and cathodes of the first gas discharge tubes and to the potentiometers and which operates upon the occurrence of the said first voltage signals at any two of those cathodes simultaneously to reduce the value of the voltage applied to the anodes of the first and second gas discharge tubes below the anode to cathode discharge maintaining value for an interval in time greater than the de-ionisation time of any of those gas discharge tubes.

25. An electrical circuit according to claim 23 in which the first and second gas discharge tubes are cold cathode gas discharge triodes.

References Cited in the file of this patent UNITED STATES PATENTS 

